You can get thick gears for the <4.10 carrier.
As for prices, pick up the phone and start calling.
FWIW, I used to have a piece of paper around here somewhere with the prices from a half-dozen different vendors back when I was regearing an axle. Prices on individual parts - install kits, yokes, lockers, gears, etc - varied *widely*. But when you tallied up the total cost to buy all the pieces from one shop, they were all within about $20 of one another.
Certainly not a rule or anything... but I just remembered that.